The present disclosure relates to an isolation structure and an image sensor having the same. In more detail, the present disclosure relates to an isolation structure for electrically isolating charge accumulation regions from each other and an image sensor having the same.
In general, an image sensor is a semiconductor device that converts an optical image into electrical signals, and may be classified or categorized as a charge coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS).
The CMOS image sensor includes unit pixels, each including a photodiode and MOS transistors. The CMOS image sensor sequentially detects the electrical signals of the unit pixels using a switching method, thereby forming an image.
The CMOS image sensor is made by forming photodiodes in or on a semiconductor substrate, forming transistors connected to the photodiodes on the semiconductor substrate, forming wiring layers functioning as signal lines connected to the transistors, and forming a color filter layer and micro lenses on or over the wiring layers.
Especially, the CMOS image sensor includes a plurality of pixel regions arranged in rows and columns, and a photodiode, a transfer gate, a floating diffusion region, etc. are formed in or on each pixel region. For example, the photodiode includes a p-type surface layer and an n-type charge accumulation region, and when incident light strikes the surface of the photodiode, electrons (photo-charges) are generated in the depletion region of the p-n junction of the photodiode. The electrons are accumulated in the n-type charge accumulation region, and then moved to the floating diffusion region through the transfer gate.
Recently, as the degree of integration of the CMOS image sensor is improved, the area of the photodiode is gradually decreased, and the sensitivity and dynamic range of the CMOS image sensor may thus be deteriorated. Further, the optical noise of the CMOS image sensor such as a cross-talk may be increased.